Roadable aircraft are well known in the art. The flying car or roadable aircraft may be defined as a vehicle, which may legally travel on roads and can take off, fly, and land as an aircraft. In practice, the vehicle usually has to be converted from a standard fixed-wing aircraft to one with sufficient roadworthiness. However, in the long history of roadable aircraft, there has yet to be one design, which has met with any significant commercial success or adaptation.
Aviation pioneer Glenn Curtiss was the first to design a flying car. However, the first flying car to actually fly successfully was built by Waldo Waterman. Waterman became associated with Curtiss while Curtiss was pioneering naval aviation at North Island on San Diego Bay in the 1910s. However, it wasn't until Mar. 21, 1937 that Waterman's Aerobile first took to the air. The Aerobile was a development of Waterman's tailless aircraft, the Whatsit. It had a wingspan of 38 feet and a length of 20 feet 6 inches. On the ground and in the air, it was powered by a Studebaker engine. It could fly at 112 mph and drive at 56 mph. While an example of the Waterman Aerobile is now in the Smithsonian Air & Space museum, the design never became commercially successful.
In 1926, Henry Ford displayed an experimental single-seat airplane that he called the “sky flivver”. The project was abandoned two years later when a test flight crashed, killing the pilot. While several designs (such as the Convair flying car and Molt Taylor's Aircar) have flown, none have enjoyed commercial success and those that have flown are not widely known to the general public.
FIG. 26 is a side view of the Aerocar, illustrating details of the design. The idea for the Aerocar occurred to its designer, Moulton (Molt) Taylor, in 1946. During a trip to Delaware he met inventor Robert E. Fulton, Jr., and became captivated by the concept of Fulton's roadable airplane, the Airphibian. Taylor immediately saw the weakness in the fixed, detachable wings of Fulton's design, and set about building his prototype Aerocar with folding wings, which he completed in 1949. After a successful demonstration flight, Molt promoted the Aerocar at aircraft and auto shows and on TV. As the flood of inquiries poured in, Molt raised money to certify the machine as an airplane, and to build four “pre-production” Aerocars for demonstrations and eventual sale.
The Aerocar is a two-place aircraft with side-by-side seating, four wheels, high, unobtrusive wings, and a single Lycoming 0-320 engine mounted over the rear wheels. The propeller is mounted at the end of a long tail cone, and the latter is angled up considerably, to provide adequate propeller clearance. Its cruise speed was 100 mph, and it initially sold for $25,000.
Aerocars represent the only FAA certified airplane in history that could also drive on the highways. Three other examples of the Model I still exist: N101D is now owned by Greg Herrick; N102D, once owned by TV host Bob Cummings, has been restored by Ed Sweeney in Black Forest, Colo.; N103D is no longer airworthy, but is owned by Mildred Felling in Grand Junction, Colo. Only one example of Model II was ever built. Now owned by Ed Sweeney, it featured tricycle landing gear and accommodated four people. Perhaps the most interesting Aerocar is the Model III. Like the Model I it has two seats and four wheels, but the wheels partially retract, thereby allowing a slightly faster cruise speed. While a number of the Aerocars were built, it was not a successful design in that it did not generate a profit or become widely adopted. The Aerocar remains more of a curiosity than a practical roadable aircraft.
While Molt Taylor did successfully build a roadable aircraft, the design has a number of technical limitations. The “car” portion of the design would never meet safety standards for automobiles today, and could not easily be made to meet such standards. In addition, to convert from flying car to roadable car required detachment of the tail and wings, as illustrated in FIG. 27. This arrangement was then towed behind the car as a single-wheel trailer configuration, which would make negotiating corners difficult, if not hazardous. The large wing surfaces, when placed in trailer configuration, would be hard to handle in crosswinds, particularly with such a lightweight “car” towing them. The long drive shaft used to connect to the tail mounted propeller also presented design and operation difficulties. It would be preferable to keep the power plant and propeller drive mechanism as compact as possible.
Another notable design, Henry Smolinski's Mizar, made by mating the rear end of a Cessna Skymaster with a Ford Pinto, disintegrated during test flights, killing Smolinski and the pilot. The pod-and-twin-boom configuration of the Skymaster was a convenient starting point for this hybrid automobile/airplane. The passenger space and front engine of the Skymaster were removed leaving an airframe ready to attach to a small car.
The Mizar was intended to use both the aircraft engine and the car engine for takeoff. This would considerably shorten the takeoff roll. Once in the air the car engine would be turned off. Upon landing the four-wheel braking would stop the craft in 525 feet or less. On the ground, telescoping wing supports would be extended and the airframe would be tied down like any other aircraft parked at the airport. The Pinto could be quickly unbolted from the airframe and driven away.
On Sep. 11, 1973, during a test flight at Oxnard, Calif., the right wing strut detached from the Pinto. Some reports say the wings folded and others say the Pinto separated from the airframe. Smolinski and the pilot, Harold Blake, were killed in the resulting fiery crash. Even though the Pinto was a light car, the total aircraft was already slightly over gross weight without passengers or fuel.
The Mizar illustrates one problem with trying to make a roadable aircraft from an automobile. Even with a detachable wing and engine structure, the overall aircraft weight is so high as to make the design impractical. As safety requirements for automobiles have increased over the years (side impact, 2.5 mph bumpers, air bags, air curtains, rollover protection, and the like) and emissions requirements have increased, the overall weight of even the smallest automobile in the United States has increased. Building attachable wings to an automobile frame is therefore not a practical solution for a roadable aircraft, due to weight considerations. In addition, requiring the user to detach wings and engine and leave them at an airport would limit the aircraft/automobile concept in use, as the pilot/driver would have to return to the airport where he left his wing/engine pod in order to take off again.
In the 1950s, Ford Motor Company performed a serious feasibility study for a flying car product. They concluded that such a product was technically feasible, economically manufacturable, and had significant realistic markets. The markets explored included ambulance services, police and emergency services, military uses, and initially, luxury transportation. Light helicopters now serve some of these markets.
When Ford approached the U.S. Federal Aviation Administration (FAA) about regulatory issues, the critical problem was that the (then) known forms of air traffic control were inadequate for the volume of traffic Ford proposed. At the time, air traffic control consisted of flight numbers, altitudes and headings written on little slips of paper and placed in a case. Quite possibly computerized traffic control, or some form of directional allocation by altitude could resolve the problems. In addition, the cost of certifying such an aircraft would be prohibitive, so Ford dropped the project.
Since that time period, a number of aviation developments have made the concept of the roadable airplane more attractive. While regulations concerning automobiles are extremely stringent and result in large weight penalties, motorcycles, defined generally as any vehicle with three wheels or less, are subject to much less government regulation and are considerably lighter on construction. Three-wheeled vehicles such as the Corbin Sparrow have been promoted as high-mileage alternatives to the traditional automobile, and may be registered as motorcycles in most States, eliminating the need for heavy and cumbersome safety and emissions gear.
In addition, the new Light-Sport Aircraft Standard recently promulgated by the FAA makes it easier to develop smaller aircraft without having to go through the tortuous process of FAR 23 certification. The Light-Sport Aircraft Standard also makes it easier to casual pilots to become registered with a Sport Pilot certificate, as opposed to the traditional and more expensive private pilot licensing process.
The Federal Aviation Administration defines a light-sport aircraft as an aircraft with a maximum gross takeoff weight of not more than 1320 pounds (600 kilograms) for aircraft not intended for operation on water; or 1,430 pounds (650 kilograms) for aircraft intended for operation on water; a maximum airspeed in level flight of 120 knots (222 km/h); a maximum stall speed of 45 knots (83 km/h); either one or two seats; fixed undercarriage and fixed-pitch or ground adjustable propeller; and a single electric motor or reciprocating engine, which includes diesel engines and Wankel engines.
Aircraft which qualify as LSA may be operated by holders of a Sport Pilot certificate, whether they are registered as Light Sport Aircraft or not. Pilots with a private, recreational, or higher pilot certificate may also fly an LSA, even if their medical certificates have expired, so long as they have a valid driver's license to prove that they are in good enough health to fly. LSA also have less restrictive maintenance requirements and may be maintained and inspected by traditionally certificated Aircraft Maintenance Technicians, by individuals holding a Repairman: Light Sport certificate, and (in some cases) by their pilots and/or owners.
In addition, new aircraft routing techniques are envisioned to make it easier to route aircraft and reduce the likelihood of collisions, without having to rely upon cumbersome manual flight guidance techniques. The future of U.S. aviation is the Next Generation Air Transportation System, or NextGen. In the 21st century, the growing global demand for aviation, development of new airborne vehicles, and security and environmental concerns, are going to require a new kind of airways system.
NextGen is a wide-ranging transformation of the entire national air transportation system—not just certain pieces of it—to meet future capacity demands and avoid gridlock in the sky and at airports. State-of-the-art technology, such as Automatic Dependent Surveillance, Mode B (ADS-B), multilateration, GPS guidance, and the like, along with new procedures, and new airport infrastructure will allow the U.S. Federal Aviation Administration (FAA) to safely handle dramatic increases in the number and type of aircraft, without being overwhelmed by congestion. NextGen is a curb-to-curb transformation of the U.S. air transportation system. This transformation involves going from today's ground-based, human-dependent communications, navigation, and surveillance system to one that takes advantage of satellite navigation and surveillance, digital communications and advanced networking. It shifts some decision-making from the ground to the cockpit.
As a result of all these changes, the possibility of implementing a true roadable aircraft are stronger than ever, provided such an aircraft can be made which is lightweight, compact, easy to use, and has attached wings and structure (as opposed to detachable wings) such that conversion from flying aircraft to roadable aircraft can be accomplished in minutes (as opposed to hours) and the resulting roadable aircraft be compact and easily driven.
Partially as a result of all these changes, a number of contemporary designs are presently being developed or proposed. Today, there is an active movement in the search for a practical flying car. Several conventions are held yearly to discuss and review current flying car projects. Two notable events are the Flying Car forum held at the world-famous EAA Airventure at Oshkosh, Wis., and the Society of Automotive Engineers (SAE) conventions held at various cities. A number of companies are developing vehicles.
Terrafugia, a private company, is developing the Transition, a roadable aircraft that the company describes as a “Personal Air Vehicle”. The aircraft is designed to change configurations, enabling it to operate as a traditional road vehicle and as a Light Sport Aircraft. The estimated purchase price is $148,000. Owners will drive the car from their garage to an airport where they will then be able to fly within a range of 100 to 500 miles. It will carry two people plus luggage and will operate on premium-unleaded gas.
The Transition, as of this date, has successfully completed almost 30 flights and is expected to be certificated as a Light Sport Aircraft sometime in 2011. The wings are hinged at the root and mid semi-span and fold upwards against the fuselage for road use. If successfully certificated, the Transition will be a significant step toward the roadable airplane reaching its potential. With a highway speed of 65 mph and airspeed of 115 mph, however, the Transition is only practical for relatively short commutes, and the wind sensitive folded wings make it unsuitable for driving on expressway. These limitations hinder its utility considerably, and may thus limit its commercial viability as well.
Retired Air Force pilot-engineer Rich Strong developed the StrongMobile Magic Dragon Aircar over a 50-year period. The design uses an automobile-type lifting body fuselage and automotive suspension. Flight propulsion uses a front-mounted ducted fan with side outlets. Automatic conversion uses a combination of folding and swinging to stow the wings into the body. The current design envisions a core market of frequent regional business travelers whose timesavings make using the StrongMobile virtually revenue neutral.
LaBiche Aerospace's FSC-1 is a developmental prototype Flying Car and is an example of a practical flying car capable of utilizing today's automotive and aviation infrastructure to provide true “door-to-door” travel. The vehicle can be parked in any garage or parking space available for cars. The FSC-1, like the Transition, will be capable of automatic conversion from aircraft to car at the touch of a button. LaBiche has flown a 1/10th scale model, tested a ¼-scale model and, as of 2006, was finishing the FSC-1 prototype for road and flight tests. Currently, the FSC-1 requires a pilot and driver's license to operate. However, upon approval from the FAA, development is underway for utilizing a new satellite-navigation “hands free” flight system to travel from airport to airport that will eliminate the need for a pilot's license. Numerous safety systems and fail-safes are also employed on the FSC-1, such as a recovery parachute.
The Haynes Aero Skyblazer is a development stage vehicle that uses a single turbofan engine to provide thrust in the air and to generate electricity to power electric motors for ground travel. In “car mode”, a patented mechanism allows the wings to fold into the body of the vehicle, which is designed to fit into a single car garage and regular parking space. In “aircraft mode” the vehicle will have STOL capabilities and be able to use almost any public-use airfield. It is expected to have a top speed of 400 mph (640 km/h) and a range of 830 miles (1,340 km). The Skyblazer team has completed wind tunnel, stability and control testing and flown a ⅙th scale model.
The Milner AirCar is an advanced composite four-door, four-passenger roadable aircraft (flying car) with foldable main wing at the rear and foldable canard in the front. The AirCar has a wingspan of 28 ft (8.5 m), maximum gross weight of 3,000 lb (1,400 kg) and a total of 300 hp (220 kW) from dual ducted fans. Cruise airspeed and range are expected to be 200 mph (322 km/h) for 1,000 miles (1,600 km). After landing the wings fold to a width of 7 ft (2.1 m) so the vehicle can drive on public roads. A drive-able, but non-flyable prototype is complete.
The Moller Skycar M400 is a prototype personal VTOL (vertical take-off and landing) aircraft that some refer to as a flying car, although it cannot be driven as an automobile. However, the Skycar is a good demonstration of the technological barriers to developing the VTOL flying car. Moller International continues to develop the Skycar M400, which is powered by four pairs of tandem Wankel rotary engines, and is approaching the problems of satellite-navigation. Moller also advises that, currently, the Skycar would only be allowed to fly from airports & heliports. Moller has been developing VTOL craft since the late 1960s, but no Moller vehicle has ever achieved free flight out of ground effect. Macro Industries Skyrider is a prototype of a flying car developed by Macro industries, which is similar to the Moller Skycar except lighter
Urban Aeronautics' X-Hawk is a VTOL aircraft, which operates much like a tandem rotor helicopter, however it doesn't have the exposed rotors, which make helicopters dangerous for personal use. This is accomplished by containing the rotors in large ‘ducts’, which make up most of the body of the craft; the requisite decrease in rotor size also decreases fuel efficiency. The X-Hawk is being promoted for rescue and utility functions. It is expected to be available for about $3 million around 2010.
MotoPOD LLC advocates the combined use of airplanes and motorcycles to achieve door-to-door transportation. The company has developed a Motorcycle Pod that allows pilots to carry a street-legal motorcycle beneath their airplane. After landing, it takes only a few minutes to remove the motorcycle, unfold the handlebars and ride away. The company believes this modular solution will appeal to pilots who currently enjoy airplanes and motorcycles separately.
PAL-V Europe BV: the PAL-V ONE is a hybrid of a gyrocopter with a car. It has three wheels and a top speed of 124 mph on land and air. It can run on gasoline, biodiesel or bio-ethanol and will cost $75 000. The vehicle has a very short take of and vertical landing capability. At less than 70 decibels it is quieter than a helicopter due to the slower rotation of the main rotor. The PAL-V ONE has only one seat.
The Wolff AeroCycle is a motorcycle that can have the airplane parts attached in order to fly, and then detached to drive on the road.
The SkyBike, by SAMSON MOTORWORKS LLC is a three-wheel concept with telescoping wings. First introduced at AirVenture 2008, the SkyBike is to utilize a single Wankel rotary engine and ducted fan to keep the propeller out of harms way on the ground. The wheels and propeller are to be powered by the same engine, but wheel-power only to be utilized on the ground. Development is ongoing at Swift Engineering of San Clemente, with flying prototype targeted for 2009. A predicted top speed of 110 mph on the ground is nearly as fast as the anticipated 130 mph in the air. No parts are left at the airport after conversion from aircraft to ground vehicle, as the main wing and tail retract into the vehicle body. The vehicle leans into the turns on the ground, to impart the feeling of being ‘flown’ on the ground as well.
While the use of telescoping wings seems to solve many of the problems of the Prior Art, it is unclear whether such wings can be made strong and light enough to practical use. Note the use of the entirely shrouded ducted fan, which appears to solve at least some of the propulsion problems of the Molt Taylor Skycar previously discussed. It is unclear whether such a fan could generate sufficient propulsion to fly the aircraft, given the extensive ducting and shrouding of the fan. In addition, with the use of such a relatively short fuselage, the issue of boundary layer separation when using a ducted fan is an issue. Note also the lack of tail surfaces for this design, which raises some stability issues.
The Parajet Skycar utilizes a paramotor for propulsion and a parafoil for lift. The main body consists of a modified dune buggy. It has a top speed of 80 mph and a maximum range of 180 miles in flight. On the ground it has a top speed of 112 mph and a maximum range of 249 miles. Parajet intends to fly and drive its prototype from London to Timbuktu in January 2009.
In order to be successful in the marketplace, a modern roadable aircraft should meet the following criteria:                The wings and power plant should remain attached to the vehicle in roadable mode, so that no parts are “left behind” at the airport.        When in roadable mode, the wings and fuselage should present a low profile to minimize the effect of crosswinds and the like.        The vehicle should be lightweight so that it may possibly registered as a Light-Sport Aircraft, in order to reduce regulatory hurdles and make it easier to become licensed to fly.        It should have fewer than four wheels, so that it may be registered as a motorcycle on the road, reducing the amount of Federal regulations required to certify such a vehicle for road use.        It should use the same power plant for road use as for flying use, to reduce weight and complexity.        
There are a number of Patents relating to roadable aircraft as well as foldable wing designs and ducted propeller designs.
Samuel, U.S. Pat. No. 5,775,249, issued Jul. 7, 1998, and incorporated herein by reference, discloses an inflatable sail for a sailboat. Although this Patent is directed toward a sailboat sail, the principles of airfoil design for aircraft may also be applied to sailboats. The internal structure is described as being either flexible or rigid, and the external covering is described in one embodiment as a solid plastic. It appears that the lateral ribs of Samuels (running the length of the wing) would prevent folding of the wing for storage. While the wing is discussed as having “inflatable” panels, no mention is made of how to maintain tension on the sailcloth.
Van Alstyne, U.S. Pat. No. 3,525,483, issued Aug. 25, 1970, and incorporated herein by reference, discloses a foldable panel for spacecraft use. The structure of this panel is not directed toward an airfoil.
Abel, U.S. Pat. No. 2,572,421, issued Oct. 23, 1951, and incorporated herein by reference, discloses a folding wing construction for an aircraft. This Patent appears to be relevant as background only, as it shows only a conventional folding and rotating wing well known in the art.
Pellarini, U.S. Pat. No. 2,674,422, issued Apr. 6, 1954, and incorporated herein by reference, discloses a folding wing construction for a roadable aircraft. This Patent appears to be relevant as background only, as it shows only a conventional folding and rotating wing well known in the art, as applied to a roadable aircraft.
De Jean, U.S. Pat. No. 2,812,911, issued Jul. 30, 1953, and incorporated herein by reference, discloses a folding wing construction for an aircraft. This Patent appears to be relevant as background only, as it shows only a conventional folding and rotating wing well known in the art.
Miller, U.S. Design Pat. No. D340,426, issued Oct. 19, 1993, and incorporated herein by reference, shows a folding wing construction for a roadable aircraft. This Patent appears to be relevant as background only, as it shows only a conventional folding and rotating wing well known in the art, as applied to a roadable aircraft.
Cams, U.S. Pat. No. 1,793,056, issued Feb. 17, 1931, and incorporated herein by reference, discloses a folding wing construction for an aircraft. This Patent appears to be relevant as background only, as it shows only a conventional folding and rotating wing well known in the art.
Zuck, U.S. Pat. No. 3,056,564, issued Oct. 2, 1962, and incorporated herein by reference, shows a folding wing construction for a roadable aircraft. This Patent appears to be relevant as background only, as it shows only a conventional folding and rotating wing well known in the art, as applied to a roadable aircraft.
McCaughan, U.S. Pat. No. 5,743,493, issued Apr. 28, 1998, and incorporated herein by reference, discloses boundary layer control in aerodynamic low drag structures. This particular boundary lawyer control is used in a jet engine nacelle. Inlet ducts are used to draw air from a fuselage or other surface to maintain boundary layer control. As such, McCaughan is no more than general background art on the use of inlets on an aircraft surface to control boundary layer separation.
Seidel, U.S. Pat. No. 6,527,224, issued Mar. 4, 2003, and incorporated herein by reference, discloses a separate boundary layer engine inlet. This Patent, assigned to Boeing, illustrates a futuristic lifting body aircraft design that Boeing has used in advertisements and promotions. Fan inlets are located in a wide horizontal slot on the upper surface of the lifting body, while engine core inlets are located above these slots.
Wagner, U.S. Pat. No. 3,012,740, issued Dec. 12, 1961, and incorporated herein by reference, shows a complicated aircraft boundary layer control system using a series of controllable suction and blowing ducts to control boundary layer air flow on wing control surfaces. This reference shows little more than controlling boundary layer airflow using ducting and airflow is known in the art. This reference has particular application to control surfaces, not to fuselage or other surfaces.
Anxionnaz, U.S. Pat. No. 3,951,360, issued Apr. 20, 1976, and incorporated herein by reference, discloses a device for regulating and recovering the boundary layer over the surface of an aircraft. This is another cumulative reference showing the use of ducting and slots to draw air in from a surface to control boundary layer separation.
Dunham, U.S. Pat. No. 3,193,215, issued Jul. 6, 1965, and incorporated herein by reference, discloses an aerodynamically designed amphibious vehicle. This is another cumulative reference showing the use of ducting and slots to draw air in from a surface to control boundary layer separation.
Hatrick et al., U.S. Pat. No. 5,730,393, issued Mar. 24, 1998, and incorporated herein by reference, discloses an aircraft propulsive power unit Like the McCaughan reference (also assigned to Short Brothers, PLC) this reference is related to jet engine nacelles. However in this Hatrick device, the goal is to disrupt the boundary layer.
Pulfreyman, U.S. Pat. No. 3,576,300, issued Apr. 27, 1971, and incorporated herein by reference, discloses a lifting body aircraft design Like the Boeing reference above, this design uses rear-mounted engines to draw the boundary layer in from the top of the lifting body.
Meister, U.S. Pat. No. 5,899,416, issued May 4, 1999, and incorporated herein by reference, discloses a rudder assembly with boundary layer control. This is another cumulative reference showing the use of ducting and slots to draw air in from a surface to control boundary layer separation.
Relkin, U.S. Pat. No. 3,599,901, issued Aug. 17, 1971, and incorporated herein by reference, discloses a vehicle for land or air travel, which is relevant as background only.
Pradip, Published European Patent Document EP 0776821, incorporated herein by reference, discloses boundary layer control for aircraft wings. This is another cumulative reference showing the use of ducting and slots to draw air in from a surface to control boundary layer separation.
Savitsky et al., U.S. Pat. No. 5,417,391, issued May 23, 1995, and incorporated herein by reference, discloses a method to control the boundary layer on an aircraft. This is another cumulative reference showing the use of ducting and slots to draw air in from a surface to control boundary layer separation.
Hatrick, U.S. Pat. No. 6,151,883, issued Nov. 28, 2000, and incorporated herein by reference, is another Short Brothers Patent directed toward thrust reversing and is deemed of limited relevance.
Taylor, U.S. Pat. No. 2,659,781, issued Sep. 1, 1953, and incorporated herein by reference, discloses boundary layer control for an aircraft. This is another cumulative reference showing the use of ducting and slots to draw air in from a surface to control boundary layer separation.
Hassan, U.S. Pat. No. 6,889,302, issued May 31, 2005, and incorporated herein by reference, discloses a method for altering boundary layer characteristics. This is another cumulative reference showing the use of ducting and slots to draw air in from a surface to control boundary layer separation.
McCormick, U.S. Pat. No. 6,390,418, issued May 21, 2002, and incorporated herein by reference, discloses a tangentially directed acoustic jet controlling boundary layer. This reference is of interest as background only. It appears to use audio speakers to direct an acoustic “jet” into the airflow.
Leray, U.S. Pat. No. 1,889,255, issued Nov. 29, 1932, and incorporated herein by reference, discloses a rotorplane. This fantastic design is clearly not practical. In one of his many embodiments, Leray discloses placing a “sucking fan” 70 into the hub of a propeller. However, this sucking fan appears to be gear driven from the propeller shaft and is very small in size. Moreover, Leray does not disclose using such a sucking fan to draw air from the fuselage of the aircraft to control boundary layer separation.
Kelley-Wickemeyer, Published European Patent Document EP 0932548, published Jan. 22, 2003, and incorporated herein by reference, discloses an aircraft with an unswept slotted cruise wing airfoil. This is another cumulative reference showing the use of ducting and slots to draw air in from a surface to control boundary layer separation.
Sorenson, Published U.S. Patent Application 2002/0139894, published Oct. 3, 2002, and incorporated herein by reference, discloses a roadable aircraft boat. This is another fantastic design, which does not seem practical. While Sorensen shows ducting drawing air in from the surface of the fuselage, it does not appear he is doing so to control boundary layers for a pusher prop design. Thus, it appears this reference is relevant as background only.